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Rat Bite Fever

Rat-bite fever is an infection that is caused by one of two different bacteria: Streptobacillus moniliformis (North America) or Spirillum minus (Asia). This infection is also referred to as Haverhill fever, epidemic arthritic erythema, spirillary fever, or sodoku, depending on where the infection was contracted. These bacteria are found in the respiratory tract, mouth, and nose of rodents, most commonly in ratsRats and other rodents are known as carriers because these bacteria are natural bacteria in their respiratory tract and they do not cause the rodent to get sick.

Who is at risk and how is it contracted?

It is an infection that has recorded cases all over the world, but it is rare. The people who live and work with rodents are at higher risk than others. Pet owners, pet store employees, laboratory technicians, HVAC professionals, and exterminators are some of the people who are at greater risk for the infection. Also, younger children, elderly, and people with compromised immune systems are at great risk as well.

Rat-bite fever is normally caused by a bite or scratch from the rodent, but there are other ways as well. Close contact can cause the infection, especially the type of contact that can happen between the rodent and the pet owner. Another way that it can be transmitted is by consuming food and drink that has been contaminated with the bacteria when it is contracted through food and drink it is known as Haverhill fever. It is not something that can be passed from person to person.


Symptoms of the infection can vary, depending on the particular bacterium that caused it or how it was contracted.

  • When it is caused by S. moniliformis, there is an incubation period of 3 to 10 days normally, but it can be as long as 3 weeks. The symptoms include fever, nausea, headache, a bumpy, red rash (that doesn’t itch), and swollen and/or achy joints.
  • When it is caused by S. minus, there is an incubation period of 7 to 21 days and the symptoms include swollen lymph nodes, fever, and swelling or open sores near the original wound site.
  • Haverhill fever happens when the bacteria is ingested in food or water and intense nausea, vomiting, and sore throat are common.

If treatment is sought quickly, the symptoms can be kept mild and the person can recover rather quickly. If it goes untreated, it can lead to other serious issues like pneumonia, meningitis, heart infections, and sepsis, and these symptoms can be fatal.

Treatment and Prevention

This infection is treated with antibiotics and these are usually effective as long as the disease has not progressed to more serious complications. If further complications arise, these symptoms will require other, more complicated treatments for each symptom.

For people who live and work with rats, they must understand how to safely interact with the animals. Don’t share food or drink, cover any cuts or sores, and wash hands before and after handling the animal and their cage. It is important to wash any bite or scratch as soon as it happens and monitor the area and any symptoms that may arise. And most importantly, avoid direct contact with any wild rat as they may carry other diseases besides rat bite fever.

Other Rat Associated Diseases